NASA has spotted something strange and beautiful in the sands of Mars—a remarkable dune field that looks eerily similar to Morse code. And it has a message for us.

The dunes in this photo were recently spotted by Hi-RISE, a visible light and near-IR camera that’s been snapping stunning portraits of the Red Planet’s surface from its perch aboard NASA’s Mars Reconnaissance Orbiter since 2006. According to Veronica Bray, the Hi-RISE targeting specialist who analyzed the image, dot and dash features like these have been spotted on Mars before. But in this photo of the Hagal Dune field just south of Mars’ north polar cap, the code-like pattern is especially clear due to unusual topography.

Specifically, a nearby circular depression (probably a sand-filled impact crater) has “focused the wind, and also limited the amount of sand available for formation of the dunes,” Bray told Gizmodo.

The dashes are formed by bidirectional winds—that is, winds coming from either direction perpendicular to the dune itself, which funnel sand into a line. The dots (technically “barchanoid dunes”) are what happens when something interrupts this line-drawing process, although the exact mechanism remains unknown. Bray, not herself a dune specialist, speculates that the barchanoid dunes could be the result of dashes getting stretched out by winds.